Alkanolamines in vinyl chloride suspension polymerization

ABSTRACT

An improved process for the suspension polymerization of vinyl chloride or mixtures thereof with vinyl acetate by conducting the polymerization in the presence of from 0.2-2.0 phm of an alkanolamine corresponding to the formula   WHERE R is hydrogen or an alkyl group of one to two carbon atoms and R1 is hydrogen or a methyl radical thereby reducing fisheye formation, and improving thermal stability.

United States Patent [72] Inventor Harry F. Kruse Terre Haute, Ind. [2]]Appl. No. 872,763 [22] Filed Oct. 30, 1969 [4S] Patented Dec. 14, 1971[73] Assignee Commercial Solvents Corporation New York, N.Y.

[54] ALKANOLAMINES IN VINYL CHLORIDE SUSPENSION POLYMERIZATION [56]References Cited UNITED STATES PATENTS 3,477,999 11/1969 Takeda et al.

Primary Examiner-Joseph L. Schofer Assistant ExaminerStanford M. LevinAttorneys-Howard E. Post and Robert H. Dewey ABSTRACT: An improvedprocess for the suspension polymerization of vinyl chloride or mixturesthereof with vinyl acetate by conducting the polymerization in thepresence of from 0.2-2.0 phm of an alkanolamine corresponding to theformula R+CH OH 1 .7 where R is hydrogen or an alkyl group of one to twocarbon atoms and R is hydrogen or a methyl radical thereby reducingfisheye formation, and improving thermal stability.

ALKANOLAMINES IN VINYL CHLORIDE SUSPENSION POLYMERIZATION BACKGROUND OFTHE INVENTION This invention relates to an improved process for theproduction of vinyl polymers. In a particular aspect, this inventionrelates to an improved process for the suspension polymerization ofvinyl chloride or mixtures thereof with vinyl acetate to producepolyvinyl chloride or copolymers of vinyl chloride and vinyl acetate inparticulate form.

Polyvinyl chloride and copolymers of vinyl chloride and vinyl acetateare used in large amounts in a variety of applications. The copolymersgenerally contain from about 5 percent to about 15 percent by weight ofvinyl acetate, usually from -12 percent. One widely used method forproducing the polymer is to effect the polymerization of the monomer inan aqueous system at elevated temperatures and under the pressure ofconfinement to produce a polymer suspension. The polymer is separated,e.g. by filtration, dried and is obtained in particulate form. TI-Iepolymer particles are then used in the preparation of sheets by millingor extruding at about 30035 0 F., until the particles are fused into asheet. If plasticized film is desired, the particles are mixed with theplasticizer before the milling or extruding step.

One of the problems encountered in utilization of vinyl polymers in theaforedescribed manner is the formation of multiple fisheyes," a fault intransparent or translucent materials especially noticeable in films orsheets. A fisheye is a small globular mass formed in the polymerizationprocess and incompletely fused with the surrounding material duringmilling or extrusion. These globules are generally considered to behighly cross-linked whereas the desired polymer is a straight chain. Thecause of formation of fisheyes is poorly understood. Typically, aproduction unit will be relatively free from difficulty for longperiods, then without apparent cause, fisheyes will be formed resultingin a large amount of rejected material.

Another problem frequently encountered is the tendency of the polymer todiscolor due to thermal instability during the polymerization step, thedrying step, and subsequent processing steps such as in milling orextruding or working the stock material. Accordingly there is anexisting and longfelt need for an additive which will effectively reducefisheye formation and improve the thermal stability of the polymer.

SUMMARY OF THE INVENTION It is an object of this invention to provide animproved process for the production of vinyl polymers.

It is another object of this invention to provide an improved processfor the suspension polymerization of vinyl chloride or mixtures thereofwith vinyl acetate.

It is a third object of this invention to provide vinyl polymers andcopolymers having reduced incidence of fisheye formation.

It is a fourth object of this invention to provide vinyl polymers andcopolymers having improved thermal stability.

Other objectives of this invention will be apparent to those skilled inthe art from the description herein.

The foregoing objectives are fulfilled by the improvement of conductingthe suspension polymerization of vinyl chloride monomer (VCM) ormixtures thereof with from about 5 to about percent by weight vinylacetate monomer, at about 60 C. in the presence of 0.2-2.0 parts perhundred parts of monomer (hereinafter abbreviated to phm) of analkanolamine corresponding to the formula:

where R is hydrogen or an alkyl group of one to two carbon atoms and Ris hydrogen or a methyl radical.

DETAILED DISCUSSION The improved process of the present inventiongreatly reduces the tendency of the formation of fisheyes and improvesthe thermal stability of the resulting polymer. According to the presentinvention, an alkanolamine corresponding to the above formula is addedto the mixture to 'be polymerized in an amount of from about 0.2-2.0phm, preferably about 0.5-1.5 phm. The polymerization is then effectedat about 60 C. in a closed reaction vessel to prevent loss of monomers(and hence under elevated pressure resulting from confinement). Thepolymerization conditions and techniques are known to those skilled inthe art.

The alkanolamines corresponding to the above formula include, but arenot limited to, monoethanolamine (MEA) 2- amino-Z-methyl-l-propanol(AMP) and Z-amino-I-butanol. AMP is preferred. These alkanolamines arecommercially available and the usual commercial grades are suitable forthe practice of this invention. AMP is also available at varyingconcentrations of -100 percent. Any of these grades is suitable providedthe water content is taken into consideration in preparing theformulation.

Vinyl chloride and vinyl acetate are commercially available rawmaterials and the usual commercial grades are suitable for the practiceof the present invention. When copolymers are prepared, vinyl acetatemonomer is usually added in an amount of from about 5 to about 15percent by weight of the vinyl chloride. Generally the preferred amountis about 10-12 percent as is known in the art.

The following recipe, which is typical of those employed in the art, wasused for the examples described hereinafter and for the controls:

The suspending agent used was methyl cellulose Methocel 60HG50,manufactured by Dow Chemical Co., Midland, Michigan. The initiator waslauroyl peroxide.

General Procedure for Conducting Polymerizations For the preparation ofvinyl chloride polymers, all the ingredients, except the vinyl chloridemonomer (VCM) were delivered to a glass pressure-resistant reactionvessel and placed in a freezer (about l0 C.) until the contents werefrozen. It was then removed from the freezer and placed on a weighingdevice.

Vinyl chloride monomer (liquefied by passing the vapors through a dryice acetone trap) was added to a few grams excess and the excess slowlyboiled off as the reaction vessel and contents warmed to roomtemperature, thereby expelling air and oxygen from the vapor space.

When the required weight was reached, the reaction vessel was thentightly closed and placed in a water bath, which was then rapidly heatedto 60 C. Mixing was produced by endover-end tumbling of the reactionvessel at 38 revolutions per minute. The polymerization reaction wascontinued overnight (ca. 16 hours) at the temperature of 60 C.

After the polymerization, the reaction vessel was cooled to below roomtemperature while still in the water bath, then removed and vented torelease any excess VCM. The pH was recorded and slurry was filtered. Theseparated polymer was repeatedly washed with distilled water and driedin a vacuum oven (30 inches of vacuum) at 50 C. until dry (percentmoisture less than 0.5 percent). They were then milled into sheets.

The results given in the examples as to thermal stability and fisheyeformation tend to be variable probably due to processing variables.However they clearly demonstrate the trends toward improved stabilityand reduced fisheye formation.

For the preparation of vinyl chloride-vinyl acetate copolymers, thevinyl acetate monomer is delivered to the reaction vessel along with thewater and other ingredients before the freezing step. The vinyl chloridemonomer is then added and the polymerization is conducted as describedabove.

EXAMPLE 1 Following the general polymerization procedure given above, anumber of runs were made with varying concentrations ofZ-amino-Z-methyl-l-propanol (AMP). The data in table 1 were detenninedon samples polymerized in 16 oz. soft-drink, pressure-resistant bottlesin the presence of 0.25 phm lauroyl peroxide initiator and 0.5 phm ofmethyl cellulose suspending agent. The data in table 2 were obtained onsamples polymerized in 12 oz. bottles at 0.18 phm of initiator. The drypolymer particles were then mixed with plasticizers and a stabilizer asfollows:

Resin 100 parts Dioctyl phthalatc 40 Epoxized soya oil Stabilizer 2 Theepoxized soya oil was Emery 9332 manufactured by Emery industries,Cincinnati, Ohio, and the stabilizer was a barium-cadmium complex,Nuodex 1237, manufactured by Nuodex Division, Tenneco Chemicals, Inc.,Elizabeth, New Jersey.

The ingredients were handmixed in a beaker, milled for 5 minutes on atwo-roll mill at 300 F., then formed into a sheet of approximately 35-40mil thickness, cooled, cut in 1 inch squares and placed in a rotatingshelf preheated oven set at 350 F. Chips were removed at various timeintervals, examined and rated for heat stability and fisheye. Fisheyewas evaluated by examining the chips for the occurrence of fisheye. Theywere rated as few, some, medium, medium high, and high. Heat stabilitywas evaluated by the time (in minutes) required for a vinyl chip tocompletely degrade (turn totally black).

The following results were obtained:

TABLE 1 Effect of AMP on Heat Stability and Fisheye Formation ThermalStability AMP. phm pH (minutes to black) Fisheye Level 0.00 3.4 I35 High0.06 4.: 120+ High 0. l 3 6.8 165+ High 0.50 9.4 135+ Medium 1.25 10.2180 Low 2.5 180+ Very few TABLE 2 Effect of AMP on Thermal Stability andFisheye Formation Thermal Stability AMP, phm pH (minutes to black)Fisheye Level 0.50 9.6 105. Some 1.0 10.0 lll Medium High 1.25 10.2 150Some 2.5 10.5 175 Some EXAMPLE 2 The experiment of example 1 wasrepeated using l2-oz. bottles and 0.18 phm initiator except thatmonoethanolamine (MEA) was substituted or Z-amino-Z-methyll-propanol.The results obtained are as follows:

TABLE 3 Effect of Manoethanolamine on Thermal Stability and FisheyeFormation EXAMPLES 3-8 The experiment of example 1 was repeated usingl2-oz. bottles except that tris(hydroxymethyl)aminomethane (TA); 2-amino-Z-methyl-l,3-propanediol (AMPD); triethanolamine;2-amino-2-ethyl-l,3 -propanediol (AEPD); and morpholine were substitutedin varying amounts for the AMP. They were relatively ineffective inreducing fisheye formation. TA, AMPD, and AEPD slightly improved heatstability at higher concentrations.

EXAMPLE 9 The experiment of example I is repeated except that 2-amino-l-butanol is substituted for AMP. It is effective in reducingfisheye formation and improving stability.

EXAMPLE 10 The experiment of example 1 is repeated except that vinylacetate monomer is substituted for 12 percent of the vinyl chloridemonomer. The copolymer obtained thereby has improved thermal stabilityand the tendency for formation of fisheye during polymerization isreduced.

lclaim:

1. in a process of the aqueous suspension polymerization of vinylchloride or a mixture thereof with from 5 to about 15 percent by weightof vinyl acetate in the presence of a suspending agent and an initiatorto produce a polyvinyl chloride or a copolymer of vinyl chloride andacetate respectively, the improvement consisting of effecting saidpolymerization at a temperature of about 60 C. in the presence of from0.2 to 2.0 phm of an alkanolamine corresponding to the formula where Ris hydrogen or an alkyl group of one to two carbon atoms and R ishydrogen or a methyl radical.

2. The process of claim 1 wherein said alkanolamine is 2-amino-2-methyl-l-propanol.

3. The process of claim 1 wherein said alkanolamine is 2- aminolbutanol.

4. The process of claim 1 wherein said alkanolamine is monoethanolamine.

5. The process of claim 1 wherein vinyl chloride is polymerized toproduce polyvinyl chloride.

6. The process of claim 1 wherein vinyl chloride is copolymerized withfrom 5 to about 15 percent by weight of vinyl acetate to produce a vinylchloride-vinyl acetate copolymer.

g;;g-; v UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION.

Patent No 3 627 742 Dated -pecember l4 1971 It is certified that errorappears in the above-identified patent and that said Letters Patent arehereby corrected as shown below:

Table 3, Column 4, line 7, in the title "Manoethanolamine" should be-Monoethanolamine--.

Claim 1, Column 4, line 47,"of", lst occurence, should be -for--. I

Claim .1, Column 4, line 51, "acetate" should be -vinyl acetate--.

Claim 3, Column 4, line 67, "Z-amino-l butanol" should be--2-amino-lbutanol-.

Signed and sealed this 27th day of June 1 972.

(SEAL) Attest:

EDWARD M.FLETCI ER,JR. ROBERT GOTTSCHALK Attesting Officer Commissionerof Patents

2. The process of claim 1 wherein said alkanolamine is2-amino-2-methyl-1-propanol.
 3. The process of claim 1 wherein saidalkanolamine is 2-amino-1-butanol.
 4. The process of claim 1 whereinsaid alkanolamine is monoethanolamine.
 5. The process of claim 1 whereinvinyl chloride is polymerized to produce polyvinyl chloride.
 6. Theprocess of claim 1 wherein vinyl chloride is copolymerized with from 5to about 15 percent by weight of vinyl acetatE to produce a vinylchloride-vinyl acetate copolymer.